Sub-caliber projectile

ABSTRACT

A projectile has a sabot including a plurality of separate angular segments secured in place around the projectile by an annular band surrounding the segments. The segments and the projectile, and the segments and the band, have intermeshing surfaces to enable thrust and spin to be imparted to the projectile by the sabot. The projectile may have a pair of such sabots, one sabot being mounted adjacent to the rear end of the projectile, and the other sabot being mounted in a forward position.

United States Patent [151 3,695,181

Bull et al. 51 Oct. 3, 1972 SUB-CALIBER PROJECTILE 1,543,035 9/ 1968 France ..lO2/93 72 l t Ge 1 V. B

[ 1 men ors 21 g k fiii i Primary Exammer-Robert F. Stahl Vt c ewpo Attorney-Stevens, Davis, Miller & Mosher [73] Assignee: Space Research Corporation, North ABSTRACT Troy A projectile has a sabot including a plurality of [22] Filed; March 12, 7 separate angular segments secured in place around the projectile by an annular band surrounding the segpp 19,057 ments. The segments and the projectile, and the segments and the band, have intermeshing surfaces to enable thrust and spin to be imparted to the projectile {521 :LS. (il. ..102/93 y the sabot The projectile may have a pair of Such I-lt. C b Sabots, one sabot being mounted adjacent to the rear [58] Field Of Search ..lO2/93 end of the projectile, and the other sabot being mounted in a forward position.

[56] References Cited FOREIGN PATENTS OR APPLICATIONS 2 Claims, 9 Drawing Figures 1,231,60l 4/1960 France ..l02/93 PATENTEDnms m2 3.695181 SHEET 2 [1F 3 FIG. 5

This invention relates to spin-stabilized sub-caliber projectiles.

As is well-known, a projectile is frequently caused to spin about its longitudinal axis as it travels along its trajectory in order to maintain the projectile on its intended course. This spin is imparted to the projectile by the rifling in the barrel from which it is fired. Also a projectile is sometimes fired from a barrel with a larger caliber than that of the projectile, for example the caliber of the projectile may be of the order of 75 percent of the caliber of the barrel. In this case, the projectile is fitted with an annular device, commonly known as a sabot, which bridges the annular gap between the projectile and the barrel. The sabot serves to correctly center the projectile in the barrel, ensures that thrust is effectively applied to the projectile, and also ensures that the necessary spin is applied to the projectile. Sabots are constructed so that they separate from the projectile under centrifugal force when the projectile leaves the barrel.

It is an object of this invention to provide a sabot construction which is relatively inexpensive, and easy to manufacture, as well as being effective in ensuring that the necessary thrust and spin are imparted to the projectile.

According to the invention, the sabot includes a plurality of separate angular segments secured in place around the projectile by an annular band surrounding the segments, the segments and the projectile and the segments and the band having intermeshing surfaces to enable thrust and spin to be imparted to the projectile by the sabot. The intermeshing surfaces may be formed by screw threads.

The projectile may be fitted with a pair of such sabots, one being located adjacent the rear end of the projectile, and the other being located in a forward position.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, of which:

FIG. 1 is a longitudinal sectional view of a projectile according to one embodiment,

FIG. 2 is a similar view of the main body of the projectile of FIG. 1,

FIG. 3 is an enlarged view of the portion of the main body indicated at A in FIG. 2,

FIG. 4 is an enlarged view of the portion of the main body indicated at B in FIG. 2,

FIG. 5 is a sectional view along the line 5-5 of FIG. 1.

FIG. 6 is a sectional view along the line 66 of FIG.

FIG. 7 is a longitudinal sectional view of a projectile according to a second embodiment,

FIG. 8 is a sectional view along the line 8-8 of FIG. 7, and

FIG. 9 is a sectional view along the line 9-9 of FIG. 7.

Referring first to FIGS. 1 to 6 of the drawings, a spinstabilized sub-caliber projectile includes a main body 1, a nose portion 2 screwed into the forward end of the body 1, and a base plug 3 screwed into the rear end of the body 1. A rear sabot 4 is located immediately adjacent the rear end of the body 1, and a forward sabot 5 is located near the front end of the body 1.

The rear sabot 4 includes three equal angular segments 6 held in place on the projectile body I by a driving band 7 encircling the segments 6. As indicated in the FIG. 3, the rear portion of the body 1 is formed with a buttress thread 8, and each segment 6 is formed with a complementary buttress thread which interrneshes with the buttress thread 8. The mutually engaging surfaces of the segments 6 and the driving band 7 are also formed with intermeshing buttress threads. It will be noted that the rear end 5 of the segments 6 provides a rear stop 9 for the driving band 7.

The driving band 7 has an annular projection 10 which engages the rifling in the barrel from which the projectile is fired to cause spin to be imparted to the sabot 4.

' Three pins 11 which key the segments 6 to the body 1 are located in equi-angularly spaced apertures 12 formed partly in the segments 6 and partly in the pro jectile body 1. Each pin 10 is retained in its aperture 12 by a plug 13 which is screw threaded into a counter bore 14 formed in the rear ends of the segments 6 and body 1. An obturator 15 in the form of a disc is secured to the rear end of the sabot 6, for example by adhesive or a weak mechanical joint.

The forward sabot 5 includes three equal angular segments 16 held in place on the projectile body 1 by an annular band 17 which functions as a bore rider to assist the driving band 7 in correctly positioning the projectile in a barrel. As indicated in FIG. 4, the relevant part of the body 1 is formed with a buttress thread 18, and each segment 16 is .formed with a complementary buttress thread which intermeshes with the buttress thread 18. The mutually engaging surfaces of the segments 16 and the bore rider 17 are formed with intermeshing stub acme threads. The rear ends of the segments 16 provide a rear stop 19 for the bore rider 17.

When the projectile assembly is positioned in a barrel ready to be fired, the forward and rear sabots 4, 5 ensure that the projectile is correctly centered in the barrel. Upon firing, thrust and spin are imparted to the projectile by the rear sabot 4, and the obturator 15 serves to reduce erosion of the barrel rifling by providing improved gas obturation.

When the projectile leaves the barrel, the bore rider 17 and driving band 7 disintegrate under centrifugal force, having been designed to do so, and the segments 6, 16 of the rear and forward sabots 4, 5 respectively then become separated from the projectile. The pins 1 1 and plugs 13 also become separated from the projectile, and the obturator 15 is also separated by air drag.

The projectile shown in FIGS. 7 to 9 has a main body 21, a nose portion 22 screwed into the forward end of the main body 21, and a base portion 23 screwed into the rear end of the main body 21. A rear sabot 24 is carried by the base portion 23 immediately behind the main body 21, and a forward sabot 25 is located near the front end of the body 21.

The rear sabot 24 includes three equal angular segments 26 held in place on the base portion 23 by a driving band 27 encircling the segments 26. The base portion 23 and segments 26 are formed with intermeshing buttress threads 26a. The driving band 27 has a trapezoidal cross-section and is located partially within a correspondingly shaped recess 28 in the periphery of the segments 26. Also, the mutually engaging surfaces of the driving band 27 and segments 26 have intermeshing peripherally extending corrugations 29.

The driving band 27 has an annular projection 30 which engages the rifling in the barrel from which the projectile is fired to cause spin to be imparted to the sabot 24 and consequently to the projectile.

Three pins 31 which key the segments 26 to the base portion 23 are located in three equi-angularly spaced apertures 32 formed partly in the segments 26 and partly in the projectile body 1. Each pin 31 is retained in its aperture 32 by the rear end of the body 1. An annular obturator 35 is mounted on the base portion 23 behind the sabot 24 by a weak mechanical joint or shrink fitting. The obturator 35 has an annular groove 35a of semicircular cross-section in its rear face.

The forward sabot 25 includes three equal angular segments 36 held in place on the body 21 by an annular band 37 which functions as a bore rider to assist the driving band 27 in correctly positioning the projectile in a barrel. The body 23 and segments 36 are formed with intermeshing buttress threads, and the bore rider 37 is a tight fit in an appropriately shaped recess in the forward end of the outer surface of the segments 36. Each segment 36 has a series of longitudinally extending apertures 38 to allow air flow therethrough and to reduce the weight of the segments 36.

It will be noted that the external diameter of the main body 21 increases from its forward end to a position approximately mid-way between the forward and rear sabots 25, 24. Rearwardly of this position, the external diameter of the body 23 remains constant for approximately one-quarter of the distance between the forward and rear sabots 25, 24, and then tapers towards the rear end of the body 23.

The projectile illustrated in FIGS. 7 to 9 operates in a similar manner to that illustrated in FIGS. 1 to 6.

It will be seen that the invention provides an extremely simple and reliable sabot arrangement for spinstabilized sub-caliber projectiles. The provision of the forward and rear sabots in the described embodiments enables the geometry of the projectile to be optimized especially since the distance between the forward and rear sabots can be relatively large,for example greater than twice the sabot caliber. For example, the muzzle velocity can be improved by reducing the shot weight, and improved aerodynamic performance can be obtained by using the most advantageous external shapes for the projectile.

The described arrangements can be designed and tested to provide a sabot-separation at the muzzle of a gun that does not increase the dispersion of the shell over that of conventional full-bore ammunition. The range capability of small guns can be increased by up to 100 percent using this system, giving the same shell fall patterns as conventional ammunition of the same range. The shell wall thickness may be tapered to match an optimization metal to high explosive ratio to provide equivalent lethality as conventional ammunition fired from the same gun.

We claim: for

l. A sub-caliber spin-stabilized projectile assembly including a projectile carrying a forward sabot on a forward portion of the projectile and a rear sabot on a rear portion of the projectile, said rear sabot including a plurality of separate angular segments surrounded by a driving band, said driving band and said angular segments separating from the projectile by centrifugal fo aft r the ro'ectile leaves the un, said drivin ba tf having me ns to engage rifling 1% a gun barrel to cause spin to be imparted to said driving band when the projectile assembly is fired from the gun, said driving band and said angular segments having inter-meshing surfaces to cause said spin to be transmitted from said driving band to said angular segments, each of said angular segments having an internal surface with a screwthread formed thereon and extending over the length of said internal surface, and said rear portion of said projectile having an external surface with a screw-thread fon'ned thereon, said screw-thread on said rear portion extending around the projectile and extending axially of the projectile for distance corresponding to the length of said internal surfaces of said angular segments, the screw-threaded internal surfaces of said angular segments inter-meshing with said screw-threaded surface of the projectile to cause said spin to be transmitted from the angular segments to the projectile, each angular segment and the projectile having a longitudinally extending aperture partly in the segment and partly in the projectile with a key being located in each aperture.

2. A projectile assembly according to claim 1 wherein each aperture has a greater portion in the segment than in the projectile. 

1. A sub-caliber spin-stabilized projectile assembly including a projectile carrying a forward sabot on a forward portion of the projectile and a rear sabot on a rear portion of the projectile, said rear sabot including a plurality of separate angular segments surrounded by a driving band, said driving band and said angular segments separating from the projectile by centrifugal force after the projectile leaves the gun, said driving band having means to engage rifling in a gun barrel to cause spin to be imparted to said driving band when the projectile assembly is fired from the gun, said driving band and said angular segments having inter-meshing surfaces to cause said spin to be transmitted from said driving band to said angular segments, each of said angular segments having an internal surface with a screwthread formed thereon and extending over the length of said internal surface, and said rear portion of said projectile having an external surface with a screw-thread formed thereon, said screw-thread on said rear portion extending around the projectile and extending axially of the projectile for distance corresponding to the length of said internal surfaces of said angular segments, the screw-threaded internal surfaces of said angular segments inter-meshing with said screw-threaded surface of the projectile to cause said spin to be transmitted from the angular segments to the projectile, each angular segment and the projectile having a longitudinally extending aperture partly in the segment and partly in the projectile with a key being located in each aperture.
 2. A projectile assembly according to claim 1 wherein each aperture has a greater portion in the segment than in the projectile. 